Cast irons, a group of iron alloys containing over 2% Carbon, among other elements, are often used to form parts or components that subsequently undergo welding processes. The welding of cast irons presents certain issues relative to forming a welded structure that exhibits a sufficient level of mechanical properties such as toughness, ductility, and resistance to cracking, among others. For example, carbides often form in a fusion zone and a mixed zone of the weld and produce a weld deposit with reduced ductility and lower strength. Additionally, it is desirable to form austenite rather than martensite in the mixed zone since austenite reduces the formation of carbides. Like carbides, martensite reduces the ductility and strength of the weld and also becomes more brittle than the surrounding material.
Additionally, the amount of arc energy required to form a fusion zone directly affects the amount of carbides that can form. Generally, a higher amount of arc energy causes more heating of the base metal, which increases the penetration of the weld metal into the cast iron base metal. The deeper the penetration, the higher the carbon content and thus an increased amount of carbide formation at the weld interface.
Accordingly, a need exists in the art for welding electrodes and weld deposit compositions that result in improved ductility, fracture toughness, and resistance to cracking, among others, in the welding of cast iron.